VLBI observations to Genesis for improved reference frames

Precise positions and velocities of globally distributed observing stations realize geodetic reference frames, which are of utmost importance for any kind of positioning and navigation on Earth and in space, as well as for the observation of minute processes, such as deformations of the Earth and sea level rise. With a global mean sea level rise of 3 to 4 millimeters per year, the terrestrial frame has to be more accurate by at least one order of magnitude to allow for an accurate determination of this effect. Within the current geodetic capabilities, however, the stability of the terrestrial reference frame is about 0.5 millimeter per year, which is the most important contribution to uncertainty in observations of sea level rise. In 2022, the Ministerial Conference of the European Space Agency (ESA) approved mission Genesis for launch in 2028. This satellite will operate at an altitude of 6000 kilometers and will be equipped with all space geodetic techniques, i.e., receivers of the Global Navigation Satellite Systems (GNSS) and the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) system, a retroreflector for Satellite Laser Ranging (SLR), and - for the first time - a dedicated Very Long Baseline Interferometry (VLBI) transmitter. In the default mode, VLBI radio telescopes observe signals from extragalactic radio sources, mostly quasars located billions of light years away. With the ESA mission Genesis, the satellite will be equipped with a special transmitter, mimicking signals from quasars at wide frequency bands and enabling VLBI observations to satellites. The feature adds a new observation type with great opportunities and challenges. This project VLBI2Genesis will address those scientific opportunities and technical challenges of the Genesis mission from a VLBI point of view. At TU Wien, we have unique tools and experience to make innovative contributions to the best-possible generation of the VLBI observations. Furthermore, we will explore concepts for observation strategies in order to get the maximum benefit for the terrestrial reference frame. And we will investigate the determination of new parameters, which have not been determined with VLBI before, such as the center of mass of the Earth. In summary, the Genesis mission is a great opportunity for a generation of scientists making unprecedented progress in the field of geodesy in general and reference frames in particular.